The present invention relates to spark plugs, and more particularly to spark plugs that may be more rapidly and easily replaced than conventional spark plugs.
Ordinary spark plugs have an external thread on a metal outer shell with a hexagonal head integrally formed with the metal outer shell and adapted for mating with a removal tool such as a socket or box end wrench. The outer shell is seated in a threaded bore of a cylinder head and may have a deformable gasket seal located between the hexagonal head and the cylinder head, thereby isolating the cylinder chamber. Complete sealing and correct positioning of a spark plug in the combustion chamber requires applying a precise torque to the hexagonal head of the spark plug. Excessive torque or incorrect positioning may strip the threads in the cylinder head, requiring expensive repairs. Space for tools is limited in many engine compartments and access is often awkward. All of the problems associated with spark plug replacement are magnified in auto racing competition where engine heat is much greater than with conventional engines and where time constraints are added. Similar problems to those discussed above are associated with the replacement of glow plugs in diesel engine applications and igniters in gas turbine engine applications.
U.S. Pat. No. 5,186,132, issued to Runge teaches a plug-in spark plug that requires a special bore in the cylinder head with a retaining groove for engaging a locking clip. The plug-in spark plug as disclosed in the Runge patent requires some sort of tool fitting in a groove to forcefully pull the plug out and a tool for engaging the clip to reduce its diameter to disengage it from the retaining area. It would be desirable to have a system that would operate with conventionally bored and threaded cylinder heads, since it would be impractical for engine manufacturers to provide special cylinder heads.
U.S. Pat. No. 3,747,583, issued to Georges and Spangler teaches a quick insertion spark plug arrangement in which an outer sleeve screws into the threaded bore in a cylinder head. The sleeve has an inner profile that cooperates with an outer profile of the plug. When in a first rotary position, the plug may be moved axially into and out of the sleeve. When the inserted plug is in a second rotary position, the outer profiles cooperate to lock the position of the plug against axial movement thus preventing the spark plug from being removed from within the sleeve.
Quick disconnect couplings for joining conduits for high pressure fluids are exemplified by U.S. Pat. No. 3,162,470, issued to Davidson, and SWAGELOK (Registered Trademark) fluid flow quick-connect coupling QF series made by the SWAGELOK company of Hudson, Ohio. Each of these couplings as disclosed include a hand-operated sliding lock sleeve that requires no tool for engagement and disengagement. This style of connection has not been applied to spark plugs, glow plugs, or gas turbine igniters.
In a conventional spark plug, the heat range or temperature of the spark plug is primarily a function of the length of the nose of the plug. It would be desirable to design a spark plug that is more efficient at controlling the heat dissipating properties of the spark plug.